From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [patch] mm: memcontrol: avoid charge statistics churn during page migration Date: Tue, 5 Aug 2014 15:34:28 +0200 Message-ID: <20140805133428.GH15908@dhcp22.suse.cz> References: <1407184469-20741-1-git-send-email-hannes@cmpxchg.org> <20140805122434.GD15908@dhcp22.suse.cz> <20140805131223.GA14734@cmpxchg.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20140805131223.GA14734-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Hugh Dickins , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Tue 05-08-14 09:12:23, Johannes Weiner wrote: > On Tue, Aug 05, 2014 at 02:24:34PM +0200, Michal Hocko wrote: > > On Mon 04-08-14 16:34:29, Johannes Weiner wrote: > > > Charge migration currently disables IRQs twice to update the charge > > > statistics for the old page and then again for the new page. > > > > > > But migration is a seemless transition of a charge from one physical > > > page to another one of the same size, so this should be a non-event > > > from an accounting point of view. Leave the statistics alone. > > > > Moving stats to mem_cgroup_commit_charge sounds logical to me but does > > this work properly even for the fuse replace page cache case when old > > and new pages can already live in different memcgs? > > We don't migrate if the new page is already charged. Right you are. Acked-by: Michal Hocko -- Michal Hocko SUSE Labs